新疆吉木萨尔凹陷二叠系芦草沟组热液喷流沉积特征及沉积环境
发布时间：2018-10-19 10:20
【摘要】：新疆吉木萨尔凹陷二叠系芦草沟组(P21)是一套非常重要的致密油层。前人研究认为芦草沟组这套层位是正常的湖相沉积,发育湖相碎屑沉积和碳酸盐沉积的过渡性岩类。根据研究团队多年来在准噶尔盆地的研究,发现吉木萨尔凹陷所处盆地的东部地区从晚石炭世至中二叠世处于陆内裂谷环境,且在沉积时期受到了岩浆热液流体的影响,形成吉木萨尔凹陷特有的热液喷流沉积环境。在该环境中除了发育正常沉积的陆源碎屑岩类外,还首次发现了与火山活动和岩浆活动相关的热液喷流沉积岩(简称“喷积岩”)。热液喷流沉积岩是与深源岩浆、热液活动相关的岩石组合:纹层状碱性-过碱性的中性(安山岩)凝灰岩类和超基性(碳酸岩)凝灰岩类,同时也发现了研究区内有丰富的藻类和生物活动的迹象。本文对吉木萨尔凹陷二叠系芦草沟组的岩石类型、矿物特征、沉积特征和形成环境进行探讨,得出以下认识:(1)热液喷流沉积岩主要分为五大类,以白云岩类和沉凝灰岩类为主。区内岩石沉积构造类型多样,主要发育水平层理和交错层理,同时也发现包卷层理、泄水构造等同生变形构造,以及本区特殊的生物成因构造。芦草沟组发育的是一套与火山活动相关的沉凝灰岩(火山碎屑岩)以及凝灰质泥晶云岩、微生物白云岩等。通过岩石学、矿物学鉴定和综合地球化学测试分析,认为本区的矿物组合是在特殊环境下形成的,与岩浆地幔热液、火山活动相关的热液喷流沉积组合。(2)根据芦草沟组岩石的地球化学实验分析,得出以下结论:①碳、氧同位素实验分析得出,研究区在沉积时期处于盐度偏高,水循环较差,蒸发速度较快的湖泊环境中,且受到了热液流体与湖水的混合作用。②根据主、微量元素实验分析,通过样品的钒(V)、镍(Ni)、锶(Sr)、钡(Ba)以及氧化还原敏感元素比值,指示其处于盐度较高、缺氧的陆相沉积环境。③稀土元素方面,样品呈现轻稀土(LREE)较为富集右倾配分模式,且出现了较弱的Ce正异常和Eu负异常的特征,反映了处在一种弱氧化的、还原的偏碱性且形成温度较低的沉积环境中。(3)芦草沟组热液喷流沉积岩层中存在一些不同于正常矿物的特殊生物形态,部分很好的保存了生物结构特征,且在生物死后被其他矿物所交代。常见到黄铁矿化、胶磷矿化、硅化的生物形态以及一些生物的空腔和骨骼碎片。通过交代矿物的结构和类型推测可能是介形虫、三叶虫等生物。这类生物主要出现在泥晶级的白云岩层中,与岩浆成因的方解石关系密切,猜测这类生物的存在也是与岩浆热液活动相关的。
[Abstract]:The Permian Lucaogou formation (P 21) in Jimusar depression, Xinjiang is a very important compact reservoir. It is considered that the Lucaogou formation is a normal lacustrine sedimentary, lacustrine clastic deposit and carbonate sedimentary transitional rock. Based on the research conducted by the research team in Junggar Basin for many years, it was found that the eastern part of the basin in the Jimusar depression was in an intracontinental rift environment from the late Carboniferous to the Middle Permian, and was influenced by magmatic hydrothermal fluid during the sedimentary period. Forming the unique hydrothermal jet deposition environment in Jimusar sag. In addition to the normal sedimentary terrigenous clastic rocks, hydrothermal jet sedimentary rocks related to volcanic and magmatic activities were first discovered in this environment. Hydrothermal jet sedimentary rocks are rock assemblages related to deep magma and hydrothermal activity: lamellar alkaline-peralkaline neutral (andesite) tuff and ultrabasic (carbonate) tuff. At the same time, there are abundant signs of algae and biological activities in the study area. In this paper, the rock types, mineral characteristics, sedimentary characteristics and forming environment of the Permian Lucaogou formation in Jimusar depression are discussed, and the following conclusions are obtained: (1) hydrothermal jet sedimentary rocks are divided into five main types, dolomite and tuff. There are various types of sedimentary structures in the area, mainly developing horizontal bedding and staggered bedding. At the same time, cogeneration deformation structures such as enclosing bedding, drainage structure, and special biogenic structures in the area are also found. The Lucaogou formation has developed a set of sedimentary tuff (pyroclastic rock) associated with volcanic activity as well as tuffaceous mudstone and microorganism dolomite. Through petrology, mineralogical identification and comprehensive geochemical testing and analysis, it is concluded that the mineral assemblages in this area were formed under special circumstances, and were associated with magmatic mantle hydrothermal solution. (2) based on the geochemical analysis of the rocks of the Lucaogou formation, the following conclusions are drawn: 1 carbon and oxygen isotopic experiments show that the studied area is relatively high in salinity and poor in water cycle during the sedimentary period. In the lake environment with fast evaporation rate, the mixing of hydrothermal fluid and lake water was carried out. 2 according to the experimental analysis of main and trace elements, the vanadium (V), nickel (Ni), strontium (Sr), barium (Ba) and the ratio of redox sensitive elements were obtained. It is indicated that the samples are in a high salinity and anoxic terrestrial sedimentary environment. 3 the samples show a relatively enriched right-dip distribution pattern of light rare earth (LREE), and show the characteristics of weak Ce positive anomaly and Eu negative anomaly. It reflects that there are some special biological forms in the hydrothermal jet sedimentary strata of the Lucaogou formation which are different from the normal minerals in a weakly oxidized, reduced alkalinity and low temperature sedimentary environment. Some of the biologic features are well preserved and are accounted for by other minerals after the death of the organism. Pyrite mineralization, phosphate mineralization, silicification, and some biological cavities and bone fragments are common. The structure and types of metasomatic minerals may be ostracods and trilobites. This kind of organism mainly appears in mud-grained dolomite strata and is closely related to the calcite of magmatic origin. It is assumed that the existence of this kind of organism is also related to magmatic hydrothermal activity.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13
，
本文编号：2280846
[Abstract]:The Permian Lucaogou formation (P 21) in Jimusar depression, Xinjiang is a very important compact reservoir. It is considered that the Lucaogou formation is a normal lacustrine sedimentary, lacustrine clastic deposit and carbonate sedimentary transitional rock. Based on the research conducted by the research team in Junggar Basin for many years, it was found that the eastern part of the basin in the Jimusar depression was in an intracontinental rift environment from the late Carboniferous to the Middle Permian, and was influenced by magmatic hydrothermal fluid during the sedimentary period. Forming the unique hydrothermal jet deposition environment in Jimusar sag. In addition to the normal sedimentary terrigenous clastic rocks, hydrothermal jet sedimentary rocks related to volcanic and magmatic activities were first discovered in this environment. Hydrothermal jet sedimentary rocks are rock assemblages related to deep magma and hydrothermal activity: lamellar alkaline-peralkaline neutral (andesite) tuff and ultrabasic (carbonate) tuff. At the same time, there are abundant signs of algae and biological activities in the study area. In this paper, the rock types, mineral characteristics, sedimentary characteristics and forming environment of the Permian Lucaogou formation in Jimusar depression are discussed, and the following conclusions are obtained: (1) hydrothermal jet sedimentary rocks are divided into five main types, dolomite and tuff. There are various types of sedimentary structures in the area, mainly developing horizontal bedding and staggered bedding. At the same time, cogeneration deformation structures such as enclosing bedding, drainage structure, and special biogenic structures in the area are also found. The Lucaogou formation has developed a set of sedimentary tuff (pyroclastic rock) associated with volcanic activity as well as tuffaceous mudstone and microorganism dolomite. Through petrology, mineralogical identification and comprehensive geochemical testing and analysis, it is concluded that the mineral assemblages in this area were formed under special circumstances, and were associated with magmatic mantle hydrothermal solution. (2) based on the geochemical analysis of the rocks of the Lucaogou formation, the following conclusions are drawn: 1 carbon and oxygen isotopic experiments show that the studied area is relatively high in salinity and poor in water cycle during the sedimentary period. In the lake environment with fast evaporation rate, the mixing of hydrothermal fluid and lake water was carried out. 2 according to the experimental analysis of main and trace elements, the vanadium (V), nickel (Ni), strontium (Sr), barium (Ba) and the ratio of redox sensitive elements were obtained. It is indicated that the samples are in a high salinity and anoxic terrestrial sedimentary environment. 3 the samples show a relatively enriched right-dip distribution pattern of light rare earth (LREE), and show the characteristics of weak Ce positive anomaly and Eu negative anomaly. It reflects that there are some special biological forms in the hydrothermal jet sedimentary strata of the Lucaogou formation which are different from the normal minerals in a weakly oxidized, reduced alkalinity and low temperature sedimentary environment. Some of the biologic features are well preserved and are accounted for by other minerals after the death of the organism. Pyrite mineralization, phosphate mineralization, silicification, and some biological cavities and bone fragments are common. The structure and types of metasomatic minerals may be ostracods and trilobites. This kind of organism mainly appears in mud-grained dolomite strata and is closely related to the calcite of magmatic origin. It is assumed that the existence of this kind of organism is also related to magmatic hydrothermal activity.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13
，
本文编号：2280846
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